In many nonwoven filtration media, large fibers are combined with smaller fibers. The larger fibers provide a skeleton structure around which the smaller fibers form a matrix. This combination allows for strength provided by the large fibers, with filtration efficiency provided by the smaller fibers. For certain of these include resins; however, this can add undesirable cost and reduction in porosity/permeability.
In some media, no resin is needed to hold the matrix together; however, one of the weaknesses of this type of design relates to the small fibers, which typically do not have bonds to each other. Accordingly, the strength of the matrix of these small fibers is relatively weak and is largely dependent on the entanglement of the fibers themselves. These weak spots, although highly local and small, can allow the small fibers to move, which can lead to reduction in long term performance and decreased durability.